1. Field of Invention
This invention relates in general to machines and engines that use the four body linkage mechanism to generate power or to do useful work, and in particular, to devices that modify the movement of the four body linkage (piston, connecting rod, crankshaft and cylinder/crankcase block) used to generate and transfer power in the internal combustion engine.
2. Description of Related Art
It is widely known that, at maximum pressure and temperature, the combustion process that occurs in the typical internal combustion engine is incomplete. The maximum thermal efficiency varies from 45-50% at peak output levels and often averages only 25% for a normal driving cycle. This includes both spark-ignition and compression-ignition engines. Basically, there are only two ways to improve engine efficiency: alter the fuel/air mixture, or alter the geometry of the linkage that is used to generate and transfer the work created during the combustion phase. You can force more fuel and air into the cylinder chamber using a turbo or supercharger and increase power, but the efficiency still remains low. Some improvements have been made using cleaner single compound fuels, like propane or alcohol, or by altering the mixture (carburetors), or fuel flow patterns (valves, cams, etc.), but the total improvements made by all these fuel/air changes have only increased engine efficiency by several percent in the past sixty years. The introduction of higher compression ratio engines is one major geometrical improvement that has occurred in this time span.
The poor thermal utilization of the internal combustion engine occurs primarily as a result of the geometry of the combustion chamber. The chamber shape is a cylinder with flattened ends. One end (head) is stationary and the other (piston) is free to move up and down. Minor variations have been tried on the shape of the end faces with only minimal success.
Our patent search turned up 45 different ideas using eccentric pin, gears and/or cams, and levers that were used in an attempt to alter the linkage movement. Only one of these claims (Stuke U.S. Pat. No. 1,553,009) made an attempt to change the vertical movement of the piston in an effort to increase the power output. Stuke used the mechanism as drawn in his patent in a context that contradicts his claim. A fractional gear ratio (2.72:1) was drawn in the Stuke patent, which takes 25 revolutions of the crankarm to repeat the stroke curve. Refer to Appendix A in our enclosed reference document "Delayed Drop Power Stroke--Five Body Linkage Mechanism" for a detailed examination and discussion of the Stuke patent.
The rest of the patents we looked at made attempts to alter the crankshaft action or to vary the stroke and/or compression ratio. Both the claims and mechanisms differ from those of our invention. None of them have succeeded in improving the mechanical or thermal efficiency of the internal combustion engine, except marginally. They are generally too complex to build economically. A complete list of the patents we examined is given in our attached reference document. Only one other patent had any relevancy to our claim (McWhorter U.S. Pat. No. 3,686,972). McWhorter recognized the importance of piston velocity, but he did not have the correct mechanism.
We contend that the moving piston is the major cause of the low efficiency obtained in the internal combustion engine. A large part of the engine inefficiency occurs because the piston is moving down, at an accelerating rate, as the fuel is combusted. The combustion chamber is being enlarged by the rotating linkage at the same time that the combustion force is being generated.
The time increment available to create a force that will sustain itself on the dropping piston and increase its momentum is very small. The crankarm angle increases 5.degree. every 200 micro-seconds (0.0002) at a rated speed of 4166 rpm. Ignition is typically initiated in spark-ignition engines at 20.degree.-25.degree. before top dead center (TDC) at rated speed and peak cylinder pressures occur between 5.degree.-15.degree. after TDC (see SAE reports 700064, 760645, 830334 and 852067), which means a 25.degree.-40.degree. crankarm arc is traversed from the start of ignition to peak pressure levels in 0.0010-0.0016 seconds at 4166 rpm. Diesel characteristics are different than the above numbers, but they also require small time increments.
Because it occurs in an expanding chamber after TDC is passed, the maximum pressure possible is reduced as the piston drops. The combustion force cannot sustain itself long enough on the piston to overcome the pressure drop created by the expanding chamber volume as the piston falls. Chamber volume percentage changes increase as the compression ratio goes up. When the combustion force contacts the piston, it cases the piston to accelerate downward at a faster rate than that generated by the momentum of the moving parts. The net effects of the rapidly expanding chamber also tends to create disruptive, vacuum type, flows in the pressure waves that are created.
If a mechanism can be installed to retard the piston from moving downward, thus slowing the velocity of its descent, over a crankarm rotation large enough to allow more combustion to occur in a chamber whose volume has been expanded by a minimal amount (less than the four body linkage), higher cylinder pressures will be achieved, along with better fuel combustion. More time and a smaller chamber will exist to generate a larger force acting on the piston. Torque output should increase.